OHC motility evoked by an external electric field was investigated with high-resolution light microscopy. It was found that OHCs have the ability to bend in response to an electric field perpendicular to the cell axis. Application of p-Hydroxymercuriphenylsulfonic acid (pHMPS), which is known to inhibit electrically evoked OHC motility, resulted in the complete inhibition of OHC bending. This observation is consistent with the idea that active OHC bending can be attributed to the same physiological mechanisms as the OHC axial movement. In addition, a new isoform of the anion exchanger 2 (AE2) protein was previously cloned by using an antipeptide antibody to the novel C- terminus. We have found evidence that such a protein is expressed in outer hair cells. The specific localization of this novel AE2 isoform is in the lateral wall and stereocilia of the OHCs. This suggests that it could be part of the molecular machinery involved in electro-mechanical and/or mechano-electrical transduction. There is increasing evidence for the presence of molecular signal transduction cascades in the organ of Corti. We studied the localization of two families of calcium-dependent protein kinases, the PKC family and three members of the family of calcium/calmodulin-dependent protein kinases. Our initial studies indicate that protein kinases appear to be selective markers of the differentiated cells of the sensory epithelium of the cochlea. We suggest this type of mapping provides a basis for functional studies involving the cellular physiology of specialized cells of the cochlea.